1. Field of the Invention
The present invention relates to an inspection hole structure which is installed on the reaction shaft ceiling of a flash smelting furnace and forms a furnace interior inspection hole. More particularly, the invention relates to an inspection hole structure for a flash smelting furnace, which has a water-cooling jacket structure.
2. Description of the Related Art
The flash smelting furnace is one of the conventionally available non-ferrous metal smelting furnaces using sulfide concentrate as a raw material. As shown in FIG. 4, the flash smelting furnace 100 comprises a reaction shaft 101, a settler 102 and an up-take 103. A concentrate burner 105 is installed in the reaction shaft 101 on the ceiling 104 thereof.
The concentrate is blown into the furnace through a concentrate burner 105. The flash smelting furnace 100 utilizes the oxidation reaction heat of the concentrate. In the case where the oxidation reaction heat alone is insufficient in heat quantity, combustion may be assisted by heavy oil or the like from the concentrate burner 105.
An inspection hole 106 for inspection and cleaning of the leading end of the concentrate burner 105 is installed on the reaction shaft ceiling 104 of the flash smelting furnace 100.
However, slag 300 deposits onto and grows on the inspection hole frame 107 forming the inspection hole 106 from the leading end of the concentrate burner 105. As a result, when performing a furnace inspecting operation such as inspection and cleaning of the leading end of the concentrate burner 105 by the use of the inspection hole 106, the cover 108 of the inspection hole could not sometimes be closed. It was difficult to peel off slag 300 adhering to the inspection hole frame 107.
The present inventors carried out repeated research efforts and experiments to solve this problem, and obtained the following findings:
(1) Deposition of slag from the leading end of the concentrate burner onto the inspection hole frame results in exposure of the castable from outside of the frame due to melting loss of the lowermost portion of the inspection hole frame made of a steel sheet by a high temperature, and slag adhering to this castable grows;
(2) Because of (1) above, it is difficult to peel slag deposit off the inspection hole frame; and furthermore,
(3) The slag deposit forms an obstacle, preventing the inspection hole cover from being closed, and causes gas leakage from the gap; and
(4) Treatment with a heat-resistant material is necessary for blocking the aforementioned gap.
The inspection hole provided in the reaction shaft ceiling of the flash smelting furnace is used for inspection and cleaning of the burner leading end, and is a very important inspection hole related with burner combustion. Since the inspection frequency is high, it is very important to keep a satisfactory field of vision and to maintain a space sufficient to permit cleaning of the burner.
Japanese patent No. 3381241 discloses installation of a water-cooling jacket around side walls of the reaction shaft and control of coating layers formed on the inner surfaces of the side walls.
The result of research and experiments carried out by the present inventors however reveals that the problem of slag deposition onto the inspection hole frame cannot be solved by the technology of Japanese patent No. 3381241.
The present inventors obtained findings that conversion of the frame of this inspection hole into cooling jackets makes it possible to inhibit growth of slag deposition, easily peel off the slag deposit and facilitate inspection and cleaning of the burner.
The present invention was developed on the basis of such novel findings of the present inventors.